The role of lesser snow geese as nitrogen processors in a sub-arctic salt marsh

Summary Ammonia volatilization losses from faeces of Lesser Snow Geese were measured during the summer of 1987 on the salt-marsh flats at La Pérouse Bay. Amounts of ammonia volatilized increased with increasing ambient temperature, and ranged from 1.0 to 15.1 mg N per 100 mg of nitrogen present as soluble ammonium ions at the start of the 8-h experiment. Using estimates of faecal deposition reported previously, the annual loss via volatilization was estimated at 0.08 g N m^-2, or 7.9% of the nitrogen present in goose faeces. Percent change in soluble ammonium ions in fresh faeces after 8 h ranged from -51.1% to +41.1%, indicating that net mineralization of organic nitrogen occurred in some of the faeces. Microbial respiration of fresh goose faeces increased exponentially with temperature. However, variable rates of net mineralization per unit rate of respiration indicated that the substrate quality affected microbial immobilization and thus net nitrogen mineralization. In feeding experiments, captive goslings grazed different types of vegetation, each with distinctive nutritional qualities. Forage quality had significant effects on goose feeding behavior and subsequent rates of nitrogen mineralization in fresh faeces. Net nitrogen mineralization rates in faeces from geese which grazed the three vegetation types ranged from 1.31 to 4.97 mg NH ₄ ⁺ –N g_DW ^-1 24 h^-1. Because plant growth in this salt marsh is nitrogen-limited, where swards are grazed, mineralization of organic faecal nitrogen represents an essential link in the maintenance of the flow of nitrogen into the sediments and the sustained growth of vegetation at a time when most required by the geese.     

Avian cholera exposure and carriers in greater white-fronted geese breeding in Alaska, USA

We conducted a 3-yr study (2001-03) on greater white-fronted geese (Anser albifrons frontalis) breeding in Alaska, USA, to determine the exposure of this population to Pasteurella multocida and the potential role of these birds as disease carriers. We tested sera from nearly 600 adult geese for antibodies to P. multocida serotype 1. We found a low prevalence (<5%) of positive antibodies in adult geese, and based on the short duration of detectable antibodies, these findings indicate recent infection with P. multocida. Prevalence was similar to serologic results from both breeding and wintering lesser snow geese. We also collected oral (n=1,035), nasal (n=102), and cloacal (n=90) swab samples to determine the presence of avian cholera carriers in this population. We were unable to isolate P. multocida serotype 1 from any of the birds sampled. Based on comparison with other waterfowl species, we concluded that these geese may be exposed to avian cholera during the winter or spring migration but are unlikely to play a significant role as carriers of the bacterium causing avian cholera.     

Declining Body Condition of Northern Pintails Wintering in the Playa Lakes Region

Abstract: Overwinter body condition (e.g., fat) provides an index to the health of northern pintail (Anas acuta) populations and may be a factor in the decline of the continental pintail population that has been previously overlooked or understated. We compared body condition between 1984–1985 and 2002–2003, and found that body condition of pintails arriving during early winter in the Playa Lakes Region (PLR) of Texas, USA, has declined by an average of 32%. Body fat levels declined at varying levels with juvenile males showing the largest decline of 41%, followed by adult females with 39%, juvenile females with 30%, and adult males with an overall 18% decline. Declines are likely related to declines in migration and wintering habitat quantity and quality within the PLR and potentially across the Central Flyway. We recommend further acquisition and management of play as to ensure that these valuable habitats remain available to provide critical habitats for migrating and wintering pintails and other waterfowl in the Central Flyway.     

Forage digestibility and intake by lesser snow geese: effects of dominance and resource heterogeneity

We measured forage intake, digestibility, and retention time for 11 free-ranging, human-imprinted lesser snow geese (Chen caerulescens caerulescens) as they consumed underground stembases of tall cotton-grass (Eriophorum angustifolium) on an arctic staging area in northeastern Alaska. Geese fed in small patches ( =21.5 m²) of forage that made up 3% of the study area and consisted of high-quality aquatic graminoid and intermediate-quality wet sedge vegetation types. Dominant geese spent more time feeding in aquatic graminoid areas (r=0.61), but less total time feeding and more time resting than subdominant geese. Subdominant geese were displaced to areas of wet sedge where cotton-grass was a smaller proportion of underground biomass. Geese metabolized an average of 48% of the organic matter in stembases and there was a positive correlation between dominance and organic matter metabolizability (r=0.61). Total mean retention time of forage was 1.37 h and dry matter intake was 14.3 g/h. Snow geese that stage on the coastal plain of the Beaufort Sea likely use an extensive area because they consume a large mass of forage and exploit habitats that are patchily distributed and make up a small percentage of the landscape. Individual variation in nutrient absorption may result from agonistic interactions in an environment where resources are heterogeneously distributed.     

Comparative survival and recovery of Ross's and lesser snow geese from Canada's central arctic

Large increases in several populations of North American arctic geese have resulted in ecosystem-level effects from associated herbivory. Consequently, some breeding populations have shown density dependence in recruitment through declines in food availability. Differences in population trajectories of lesser snow geese (Chen caerulescens caerulescens; hereafter snow geese) and Ross's geese (C. rossii) breeding in mixed-species colonies south of Queen Maud Gulf (QMG), in Canada's central arctic, suggest that density dependence may be limiting snow goose populations. Specifically, long-term declines in age ratios (immature:adult) of harvested snow geese may have resulted from declines in juvenile survival. Thus, we focused on juvenile (first-year) survival of snow and Ross's geese in relation to timing of reproduction (annual mean nest initiation date) and late summer weather. We banded Ross's and snow geese from 1991 to 2008 in the QMG Migratory Bird Sanctuary. We used age-structured mark-recapture models to estimate annual survival rates for adults and juveniles from recoveries of dead birds. Consistent with life history differences, juvenile snow geese survived at rates higher than juvenile Ross's geese. Juvenile survival of both species also was lower in late seasons, but was unrelated to arctic weather measured during a 17-day period after banding. We found no evidence of density dependence (i.e., a decline in juvenile survival over time) in either species. We also found no interspecific differences in age-specific hunting vulnerability, though juveniles were more vulnerable than adults in both species, as expected. Thus, interspecific differences in survival were unrelated to harvest. Lower survival of juvenile Ross's geese may result from natural migration mortality related to smaller body size (e.g., greater susceptibility to inclement weather or predation) compared to juvenile snow geese. Despite lower first-year survival, recruitment by Ross's geese may still be greater than that by snow geese because of earlier sexual maturity, greater breeding propensity, and higher nest success by Ross's geese. © 2012 The Wildlife Society.     

Associations between body composition and helminths of lesser snow geese during winter and spring migration

Costs of parasitism are predicted to be higher with greater parasite intensities and higher inter-parasite competition (diversity). We tested whether greater helminth intensities and diversity were associated with poorer body composition (whole-body fat, protein, mineral and true body mass) in lesser snow geese, Chen caerulescens caerulescens. As part of a larger study on nutritional ecology, 828 wintering or migrating geese were shot between January and May 1983 in 27 different date-locations (samples) during their northward migration through mid-continental North America. A large proportion of overall variation in body composition and parasite communities was among samples, so we analyzed data within each of the 27 samples, controlling for structural body size (the first principal component of 10 body size measurements), sex and the age of geese. There was no compelling evidence that cestodes, trematodes or helminth diversity were associated with variation in body composition but nematodes had several negative associations with fat reserves. However, negative associations between fat reserves and nematodes occurred most often in geese collected between March and May when nematode prevalences and intensities were relatively low. This suggests several possibilities: that the most common nematodes (Heterakis dispar and Trichostrongylus tenuis) were more virulent at this time, that infected individuals had been chronically infected and suffered cumulative nutrient deficits that lasted until late in the spring migration, or that geese became more vulnerable to the effects of parasites at this time of year, possibly because they redirected resources away from immunity toward fat storage in preparation for reproduction.     

Decadal changes in vegetation of a subarctic salt marsh used by lesser snow and Canada geese

In the Hudson–James Bay system, grubbing and grazing by lesser snow geese have resulted in severe devegetation of coastal marshes. These changes likely represent an example of an alternative stable state; however, long-term datasets documenting whether revegetation is occurring are scarce. Here, we report results of a 10-year study investigating changes in the state of a degraded salt marsh system on the north coast of Akimiski Island, Nunavut. Four transects were intensively sampled in 1998 and 2008, two within the dense nesting and brood-rearing area of a snow geese colony, one on the colony edge, and one outside it; all of these sites were also used by broods of Canada geese. Key forage species (Puccinellia phryganodes, Festuca rubra, Carex subspathacea) were less common near the colony center than elsewhere; biomass of Puccinellia also tended to be lower in more central areas. Forage species often increased in abundance between samplings, but the magnitude of changes was small. In contrast, non-forage species (Salicornia, Spergularia, Glaux) often reached high abundance within the colony center; some (Salicornia) decreased while others (Spergularia) increased. We argue the degraded state was initiated by foraging damage from an exceptional stopover of 295,000 staging birds in 1972 and that the combined foraging pressure of relatively small numbers of nesting and migrant geese since then, coupled with soil changes, has been sufficient to maintain devegetated areas as a persistent alternative state. Whether or not this state is truly stable, further recovery is likely to be very slow.     

Prediction of reproductive success and failure in lesser snow geese based on early season climatic variables

The North American mid-continent population of lesser snow geese (Anser caerulescens caerulescens) breeds in coastal areas of the Hudson Bay region. Breeding success is highly variable, particularly during recent decades. The availability of long-term data sets of weather and the breeding success of geese allowed us to determine whether climatic variables in spring and early summer (May–June) are reliable predictors of different attributes of the reproductive biology of snow geese. A large region of strong anomalous cooling in north-eastern North America has been the dominant anomalous climatic feature since the mid-1970s. The cooling which becomes established during winter persists into spring and early summer when migration, nesting and hatching of geese are occurring. Redundancy analysis (RDA) of the data sets was made to identify dominant correlations and regression relationships between climatic and goose variables. Individual goose response variables were further explored with stepwise multiple regression and bipartial regression. 96.7% of year-to-year variance in the goose data was explained by the selected climatic data. The first four orthogonal axes out of seven possible axes explained 92.2% of the total variance. Date of last snow on the ground and mean daily temperature from 6 to 20 May formed the lowest and highest predictor scores, respectively. Initiation date and hatching date at the low end and total clutch size and clutch size at hatch at the high end were associated with these extremes, particularly in certain years. Days of freezing rain in May and total rainfall were correlated with nest failure. Bivariate correlation/regression showed that the most parsimonious model for nest initiation day was based on four climatic predictors, for hatching day four predictors, and for clutch size at hatch, nine predictors. Both the multiple regression analyses and the redundancy analyses confirm the high degree of predictability of goose reproductive variables from selected climatic variables. As discussed, the correlations reflect both direct and indirect effects of climate on the reproductive biology of geese. The correlations are strongest in the early season and weaken by early summer.     

The early bear gets the goose: climate change,polar bears and lesser snow geese in western Hudson Bay

As climate change advances the date of spring breakup in Hudson Bay, polar bears are coming ashore earlier. Since they would have lost some of their opportunities to hunt ringed seals from a sea ice platform, they may be deficient in energy. Subadult polar bears appear to come ashore before more mature individuals and the earliest subadults are beginning to overlap the nesting period of the large colony of snow geese also occupying the Cape Churchill Peninsula. The eggs these bears are known to eat could make up some of their energy shortfall. The earlier these eggs are consumed during the snow goose nesting period, the greater would be the energy that is available. Recent studies have shown that the annual survival rate for subadult bears declined in contrast to that of prime aged individuals. If this reduction in survival is related to an increasing energy deficit, as suggested by some, the consumption of goose eggs may reverse the trend and help stabilize the population, at least for some period of time. The total number of polar bears that could benefit from this resource will depend on the increasing temporal overlap with the nesting period and on the foraging behaviors of individuals eating the eggs. It is likely that other food sources will also have to play a role if the polar bears are to persist.     

Climate change,phenology, and habitat degradation: drivers of gosling body condition and juvenile survival in lesser snow geese

Nesting migratory geese are among the dominant herbivores in (sub) arctic environments, which have undergone unprecedented increases in temperatures and plant growing days over the last three decades. Within these regions, the Hudson Bay Lowlands are home to an overabundant breeding population of lesser snow geese that has dramatically damaged the ecosystem, with cascading effects at multiple trophic levels. In some areas the overabundance of geese has led to a drastic reduction in available forage. In addition, warming of this region has widened the gap between goose migration timing and plant green‐up, and this ‘mismatch’ between goose and plant phenologies could in turn affect gosling development. The dual effects of climate change and habitat quality on gosling body condition and juvenile survival are not known, but are critical for predicting population growth and related degradation of (sub) arctic ecosystems. To address these issues, we used information on female goslings marked and measured between 1978 and 2005 (4125 individuals). Goslings that developed within and near the traditional center of the breeding colony experienced the effects of long‐term habitat degradation: body condition and juvenile survival declined over time. In newly colonized areas, however, we observed the opposite pattern (increase in body condition and juvenile survival). In addition, warmer than average winters and summers resulted in lower gosling body condition and first‐year survival. Too few plant ‘growing days’ in the spring relative to hatch led to similar results. Our assessment indicates that geese are recovering from habitat degradation by moving to newly colonized locales. However, a warmer climate could negatively affect snow goose populations in the long‐run, but it will depend on which seasons warm the fastest. These antagonistic mechanisms will require further study to help predict snow goose population dynamics and manage the trophic cascade they induce.     

The palatability of Arctic willow for greater snow geese: the role of nutrients and deterring factors

Temporary feeding on willow buds and leaves by nesting greater snow geese provided us with an opportunity to test the relative importance of nutrients and deterrents in affecting the palatability for geese of a food plant with a high phenol content. Protein, total phenol and fiber (neutral and acid detergent fiber, and lignin) were analyzed in closed and open buds and in rolled and open leaves. Geese feed on willows at the open-buds and rolled-leaf stages but not at the closed-bud and open-leaf stages. Protein content was higher in open buds and rolled leaves (25–27%) than in closed buds and open leaves (19–21%). Phenol content increased during leaf emergence but was already high (14%) in rolled leaves. All plant fibers were very high in closed buds but declined rapidly during leaf emergence. The increase in phenol: protein ratio appeared to be more important than phenol concentration alone in explaining the cessation of feeding by geese on willow leaves whereas the high fiber content of closed buds may explain why they were not eaten. Our results illustrate the value of a multifactorial approach in the study of the food selection process in herbivores.     

Explaining co-occurrence among helminth species of lesser snow geese (Chen caerulescens) during their winter and spring migration

The digestive tracts of 771 lesser snow geese (Chen caerulescens) collected from January to May 1983 from 12 locations (27 samples) were examined for helminth parasites to determine whether parasite species present in wintering geese or in spring migrants occurred independently of each other. Nine helminth species were identified. Seven had mean prevalences >5% and were the focus of this study. Six of those species were waterfowl generalists, one was a goose specialist. Our primary objective was to assess the potential contribution of factors, other than species interactions, in determining patterns of co-occurrence between helminth species. There were few negative relationships between helminth species, regardless of whether presence-absence or abundance data were used. However, some species pairs showed recurrent and significant co-occurrences. There were similar and significant effects of timing of sampling, host gender, and host age, on prevalence and mean abundance of particular species. Co-occurrences were found for those species that showed seasonal declines in prevalence, for those expected to have high colonizing ability based on host age profiles (using abundance data), and for abundant species that may have shared vectors or environmental conditions favorable for transmission. Thus, similarities between parasites in their abundance, transmission biology, and phenology seem sufficient to explain species co-occurrences without invoking other processes such as species interactions. Received: 18 March 1996 / Accepted: 20 April 1999     

The role of phenolic compounds and nutrients in determining food preference in greater snow geese

Summary We tested Buchsbaum's hypothesis that food palatability in geese is determined by a hierarchy of feeding cues among which deterrent secondary metabolites (mostly phenols) have a primary role (Buchsbaum et al. 1984). In preference tests, greater snow goose feeding was slightly depressed when grass was sprayed with ferulic acid but not when grass was sprayed with p-coumaric and tannic acids. Extracts of Timothy grass, red clover or alfalfa sprayed on grass also failed to depress goose feeding. In a multifactor experiment, phenol and protein content and height of grass were manipulated simultaneously. When ferulic acid was sprayed, protein and phenol content interacted in determining goose feeding preferences; protein content had no effect in the absence of phenol but did have an effect when phenol was added. When tannic acid was used in a similar experiment, results were inconclusive because of a significant and complex interaction between protein content and height of grass. Our results generally failed to support Buchsbaum's hypothesis that phenol content of plants has a primary role in determining food preference in geese. Protein content of plants seemed to be a more important factor.     

An outbreak of fowl cholera in waterfowl on the Chesapeake Bay

An outbreak of fowl cholera (Pasteurella multocida infection) occurred in waterfowl wintering on the Chesapeake Bay during February to March 1970. Losses were primarily confined to sea ducks: oldsquaws (Clangula hyemalis), white-winged scoters (Melanitta deglandi), goldeneyes (Bucephala clangula), and buffleheads (Bucephala albeola).     

Avian influenza shedding patterns in waterfowl: implications for surveillance, environmental transmission, and disease spread

Despite the recognized importance of fecal/oral transmission of low pathogenic avian influenza (LPAI) via contaminated wetlands, little is known about the length, quantity, or route of AI virus shed by wild waterfowl. We used published laboratory challenge studies to evaluate the length and quantity of low pathogenic (LP) and highly pathogenic (HP) virus shed via oral and cloacal routes by AI-infected ducks and geese, and how these factors might influence AI epidemiology and virus detection. We used survival analysis to estimate the duration of infection (from virus inoculation to the last day virus was shed) and nonlinear models to evaluate temporal patterns in virus shedding. We found higher mean virus titer and longer median infectious period for LPAI-infected ducks (10-11.5 days in oral and cloacal swabs) than HPAI-infected ducks (5 days) and geese (7.5 days). Based on the median bird infectious dose, we found that environmental contamination is two times higher for LPAI- than HPAI-infectious ducks, which implies that susceptible birds may have a higher probability of infection during LPAI than HPAI outbreaks. Less environmental contamination during the course of infection and previously documented shorter environmental persistence for HPAI than LPAI suggest that the environment is a less favorable reservoir for HPAI. The longer infectious period, higher virus titers, and subclinical infections with LPAI viruses favor the spread of these viruses by migratory birds in comparison to HPAI. Given the lack of detection of HPAI viruses through worldwide surveillance, we suggest monitoring for AI should aim at improving our understanding of AI dynamics (in particular, the role of the environment and immunity) using long-term comprehensive live bird, serologic, and environmental sampling at targeted areas. Our findings on LPAI and HPAI shedding patterns over time provide essential information to parameterize environmental transmission and virus spread in predictive epizootiologic models of disease risks.     

Energetics of reproduction in female and male greater snow geese

Arctic-nesting geese are classified as capital breeders (i.e., birds that rely largely on endogenous reserves to meet the high nutrient requirement of clutch formation) as opposed to income breeders (those that rely directly on ingested food). However, some evidence has suggested that energy reserves of greater snow geese (Chen caerulescens atlantica) are not sufficient to meet these costs. We tested whether greater snow geese were capital breeders and examined the consequences on their reproductive strategy. We collected 48 females and 47 males from arrival at the breeding colony on Bylot Island (NWT) to the postlaying stage, and determined fat and protein content in somatic and reproductive tissues. Rapid follicular growth was initiated only after arrival on the breeding ground. Somatic fat of females tended to increase during the prelaying and laying stages at the same time that most of the fat was deposited in developing follicles. Decrease in somatic fat in postlaying females was mostly related to its use for meeting metabolic requirements during early incubation. Hence, almost all fat invested in the clutch came from food intake, not endogenous reserves. Somatic protein was maintained during prelaying but decreased during laying, suggesting that some protein reserves were deposited in the eggs. There was no relationship between somatic fat and the number of developing follicles (incubating females excluded) but a relationship was found with somatic protein. Clutch size was not related to body size. In males, somatic fat, which was similar to females at arrival, was almost completely depleted by the postlaying stage. Male somatic protein remained stable. Male somatic reserves were not related to the somatic reserves, clutch size or nutrient investment in reproduction of their mate. We conclude that, in female greater snow geese, little fat reserves (if any) were used for egg formation though some protein reserves were used, whereas males relied heavily on their fat reserves during the same period. This is probably a consequence of the long and costly migration between the last staging area and the breeding grounds.